The present invention generally pertains to systems for obtaining a vertical profile of water quality in a body of water and is specifically directed to such a system which is capable of long term unattended operation.
In a typical prior art system a sensor for sensing predetermined characteristics of water, such as temperature, conductivity, pH, etc., is attached to a cable and deployed in and retrieved from a body of water by a winch assembly attached to the cable. The winch assembly includes a drum for receiving the cable and a motor that is coupled to the drum for driving the drum to retrieve the cable. The motor typically is an AC motor which is energized by a generator and controlled by a motor controller.
Such a system usually has been operated from a boat and has been attended by personnel during such operation.
It sometimes is desirable to obtain water quality profile measurements from bodies of water over an extended period of time and in locations when manned operation of the system is extremely expensive. Accordingly, it is preferable to be able to provide a water quality profile system which is capable of unattended operation.
A survey of manufacturers of hydrographic winch assemblies has revealed that prior art commercially available winches are unsuited for low energy consumption, long term, unattended operation aboard buoys. In fact, all such prior art commercially available winch assemblies require operator supervision.
A water quality profile measurement system capable of unattended operation was mounted on a buoy and employed by the Scripps Institution of Oceanography, La Jolla, California, some years ago. In the Scripps system the winch assembly included a narrow drum having large flanges for receiving the cable, a lead sheave for guiding the cable to and from the drum, and located a sufficient distance from the drum to enable proper cable spooling on the drum, a DC motor coupled to the drum for driving the drum to retrieve the cable; a worm gear assembly for coupling mechanical power provided by the motor to the drum at a low speed and high torque; a battery for providing energy for the motor and a motor controller coupled to the battery for controlling the motor. However, the efficiency and energy demands of the Scripps system were such that it was not capable of unattended operation over an extended period of time.